Stereo vs. Mono Bass

RBFC

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I believe Lee is asking about a single sub run stereo by having each coil receive a signal as opposed to both coils driven with the same signal and not having two subs.

I've only used a single sub for LFE so typically it's been a Y-splitter to feed both voice coils. For music I've always used one sub per channel. As such I have little idea between the differences between a single sub run stereo vs mono. Bass heavy instruments are usually panned to the center so my guess would be that there wouldn't be much difference when it comes to music.

I have a combination music/HT system. I am asking about using two (2) JL Audio subwoofers ( which I already own ) and hooking them up so that each sub plays the low bass of one stereo channel. So, there is a subwoofer for the left channel and a subwoofer for the right channel. In Home Theater use, they will both play the LFE channel if I simply select "no subwoofer" in the system setup. LFE is redirected to the mains if no subwoofer is chosen. Since I have two pairs of main outputs on the pre/pro, this is not a difficult setup choice. The level and phase adjustments will take a bit of work, but I will do it if it could provide a benefit.

At this point, it seems like an experiment worth trying. I'd still be interested in other opinions!

Lee
 

LL21

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Lee,

Definitely agree it is worth going...pls post your findings when you can! Enjoy!
 

LL21

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Steve Williams

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I have a combination music/HT system. I am asking about using two (2) JL Audio subwoofers ( which I already own ) and hooking them up so that each sub plays the low bass of one stereo channel. So, there is a subwoofer for the left channel and a subwoofer for the right channel. In Home Theater use, they will both play the LFE channel if I simply select "no subwoofer" in the system setup. LFE is redirected to the mains if no subwoofer is chosen. Since I have two pairs of main outputs on the pre/pro, this is not a difficult setup choice. The level and phase adjustments will take a bit of work, but I will do it if it could provide a benefit.

At this point, it seems like an experiment worth trying. I'd still be interested in other opinions!

Lee

Lee

mine is wired in exactly the fashion you suggested
 

garylkoh

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Sep 6, 2010
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I have a combination music/HT system. I am asking about using two (2) JL Audio subwoofers ( which I already own ) and hooking them up so that each sub plays the low bass of one stereo channel. So, there is a subwoofer for the left channel and a subwoofer for the right channel. In Home Theater use, they will both play the LFE channel if I simply select "no subwoofer" in the system setup. LFE is redirected to the mains if no subwoofer is chosen. Since I have two pairs of main outputs on the pre/pro, this is not a difficult setup choice. The level and phase adjustments will take a bit of work, but I will do it if it could provide a benefit.

At this point, it seems like an experiment worth trying. I'd still be interested in other opinions!

Lee

Lee, that is what I would do too. If you are playing vinyl, even if the subs are fed left and right channels, it would be the same as records are cut with mono bass anyway. Moving the subs around to control the modes of your room, and then adjusting the level then phase to suit your listening position I think is a very worthwhile exercise for great benefit. The JL Audio subwoofers will provide you with ample adjustment to do everything you need.
 

cjfrbw

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Apr 20, 2010
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It strikes me that with left and right discreet bass modules, you are actually WANTING phase reinforcement and interference with the idea that it improves directional cueing.

This tends to be the opposite of using multiple bass modules to reduce nulls and peaks for bass smoothing purposes in particular acoustic environments.

I suppose you would also need sources that actually can exploit right and left bass effects. I have never heard of any recording that explicitly do this, but I suppose they might exist.

With vinyl, it tends to be pointless, since for recording and cutting purposes, most vinyl deep bass is mono.

Also, I think that virtually all spatial cueing from bass comes from the bits of sound that represent percussive effects and are in the higher midrange or upper midrange.

All in all, left and right bass done properly might be a long run for a short slide, and has the potential to do as much harm as good by exacerbating room modes and actually defeating the ability of multiple bass modules to smooth the bass response from room effects.

My vote is for multiple subs with mono bass crossed over below 80Hz.
 

RBFC

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It strikes me that with left and right discreet bass modules, you are actually WANTING phase reinforcement and interference with the idea that it improves directional cueing.

This tends to be the opposite of using multiple bass modules to reduce nulls and peaks for bass smoothing purposes in particular acoustic environments.

I suppose you would also need sources that actually can exploit right and left bass effects. I have never heard of any recording that explicitly do this, but I suppose they might exist.

With vinyl, it tends to be pointless, since for recording and cutting purposes, most vinyl deep bass is mono.

Also, I think that virtually all spatial cueing from bass comes from the bits of sound that represent percussive effects and are in the higher midrange or upper midrange.

All in all, left and right bass done properly might be a long run for a short slide, and has the potential to do as much harm as good by exacerbating room modes and actually defeating the ability of multiple bass modules to smooth the bass response from room effects.

My vote is for multiple subs with mono bass crossed over below 80Hz.

This is how I have set up my system for quite some time. I have the mains crossed over to the subs at 80 Hz, and have the subs level/phase adjusted for that configuration. That's why I am seeking opinions, to better understand what performance improvements and degradations I might encounter.

Thanks,

Lee
 

Mark Seaton

WBF Technical Expert (Speaker & Acoustics)
May 21, 2010
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This topic always gets messy in discussion as posters inevitably are focused on differing aspects. The reality is that unless you are outdoors and have huge subwoofers with tons of headroom, you are battling many compromises.

Let's first look at localization. There are two considerations here. One is the ability to locate the origin of a LF source in isolation, playing by itself. The other case is one of precedence effect vs. the main speakers the subwoofers are playing in concert with. The precedence effect is what is taken advantage of to implement delay lines of speakers in large auditoriums where the main cluster of speakers reaches the far listener, but at a lower level or lacking the clarity and ineligibility which is desired. System designers will then add a delay ring of speakers closer to these far listeners. The speaker directly in front of the listener is delayed sufficiently to allow the direct sound from the main speaker cluster to arrive first. For our sensitive hearing range, it is generally accepted that a later arriving sound has to be ~10dB louder before we localize the origin of the sound to that of the late arriving speaker.

In the case of a stereo system, the low pass filtering which limits high frequencies in the subwoofer simultaneously adds increasingly more group delay to the subwoofer as the frequency is lowered or a steeper slope is selected. The main speaker's crossover design, low frequency design type and low frequency extension all contribute to how much the crossover range lags the highest frequencies, which is also why there is no perfect crossover function for all subwoofer-speaker systems. In short, sounds you might be able to localize with just subwoofers, will often not be easy to locate when the main speakers are also contributing.

This is not to say we cannot locate a subwoofer's location. Distortion products and room acoustic interactions play significant roles in this. Obviously if you can't localize a subwoofer on its own, you won't localize it with the main speakers playing, but do remember that when working optimally, the contribution of the speakers play a significant role in what is functionally practical and what can still work extremely well.
 

mep

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I bet you started with a high crossover point and went down. Everybody does!



Not I. I always start low and stay low with the crossover point. For me, that is the whole point.
 

audioguy

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Also the sub can"excite" objects close to it. That can give away its position.

I have a sub located in each of the approximate 4 corners of the room. The response from the two subs on the right is virtually identical to the two subs on the left as is the response from either pair of diagonal subs. When I only run two subs (for experimental purposes only), I use the diagonal corners and crossover at 80hz or below and can never locate the subs. BUT, if I use two subs on one side of the room, I can always locate them. Why? Because the wave launch comes from one side of the room and you could easily sense it in your body. I could not actually HEAR the subs, but it was very obvious (and somewhat unsettling) to "feel" them. There was another individual in the room at the time and he, too, could "localize" the subs.

When the two subs were in front of the room, I was not able to localize them if they were in opposite front corners (I sit about 14 feet from the sub position). When they were behind me (maybe 10 feet away) I could sense them (not hear them) on occasion as well.
 

RBFC

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BUT, if I use two subs on one side of the room, I can always locate them. Why? Because the wave launch comes from one side of the room and you could easily sense it in your body. I could not actually HEAR the subs, but it was very obvious (and somewhat unsettling) to "feel" them. There was another individual in the room at the time and he, too, could "localize" the subs.

When the two subs were in front of the room, I was not able to localize them if they were in opposite front corners (I sit about 14 feet from the sub position). When they were behind me (maybe 10 feet away) I could sense them (not hear them) on occasion as well.

This phenomenon is at the core of my question. Is this "localization" ability important to actual content in music and home theater? If I have my right main speaker and my right subwoofer level and phase aligned ( by inverting the phase of the main speaker, playing a tone at the crossover frequency and adjusting for null output ), will any musical bass or home theater effects be more "realistic"?

Let's say that the room doesn't introduce terrible anomalies with single-point source bass as opposed to twin mono sources.....

Lee
 

DonH50

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Ahah! Yes, i understand now. Thanks, Don. That nuance had not occured to me, as I have 2 preouts...one for my amp...and i run the other preout (L&R) to my one sub.

are you saying if i do 2 subs, i can run R to one sub and L to the other sub...and that will be ok? And i can leave the other set of pre-outs to go straight to my amp. Is this right?

Yes, that is what I call "stereo" subs. The normal HT configuration is to take the sub output (which is not in general just LFE) and split to two subs, a configuration I called dual-mono as two independent subs are fed the same signal. Neither way is "wrong" or "right" -- it is up to your hearing and preferences. There are advantages and disadvantages to either approach.

If you can localize the sub and run in stereo, then the subs must be near the mains or appropriately aligned so that the sub and mains are carefully aligned. If you cannot, then placement becomes less important, though time-aligning the signal so it is in phase with the mains at the crossover frequency and at the listening position is still important IME/IMO. If the subs are crossed over low enough to not be locatable (is that a word?), then you can move them in the room to provide the best frequency response at the listening position. In that case, using dual-mono (or multiple subs all fed the same starting signal), appropriately delayed and level-matched), can be a help.

One thing I did not mention is that "localization" is, to me anyway, a steady-state thing. That is, run a signal and see if you can find the sub. Pulse or transient testing yields different results as the initial pressure wave can often be readily located (it has higher frequency content by definition). That gets to be a tricky trade among position, crossover frequency and slope, etc. A lower, steeper crossover makes such a transient harder to hear (from the sub).

All IMO - Don
 

LL21

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Yes, that is what I call "stereo" subs. The normal HT configuration is to take the sub output (which is not in general just LFE) and split to two subs, a configuration I called dual-mono as two independent subs are fed the same signal. Neither way is "wrong" or "right" -- it is up to your hearing and preferences. There are advantages and disadvantages to either approach.

If you can localize the sub and run in stereo, then the subs must be near the mains or appropriately aligned so that the sub and mains are carefully aligned. If you cannot, then placement becomes less important, though time-aligning the signal so it is in phase with the mains at the crossover frequency and at the listening position is still important IME/IMO. If the subs are crossed over low enough to not be locatable (is that a word?), then you can move them in the room to provide the best frequency response at the listening position. In that case, using dual-mono (or multiple subs all fed the same starting signal), appropriately delayed and level-matched), can be a help.

One thing I did not mention is that "localization" is, to me anyway, a steady-state thing. That is, run a signal and see if you can find the sub. Pulse or transient testing yields different results as the initial pressure wave can often be readily located (it has higher frequency content by definition). That gets to be a tricky trade among position, crossover frequency and slope, etc. A lower, steeper crossover makes such a transient harder to hear (from the sub).

All IMO - Don

Wow! Thanks for taking the time!
 

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